Speed is the ratio of the distance an object moves to a. the direction the object moves. b. the amount of time needed to travel the distance. c. the motion of the object. d. the displacement of the object.

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me

a. vertically

explanation:

i tried it and took the test

if im wrong then we have different tests